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    <!-- js严格 -->
    <script>
      // 1. 定义变量, 变量类型  变量明 = 变量值

      var score = 65;
      var num = 1;
      if (score > 60 && score < 70) {
        alert('>60 and <70');
      } else if (score > 70) {
        alert('>70');
      } else {
        alert('不及格<=60');
      }
    </script>
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